Method of welding



June 1965 R. D. BREMER ETAL 3,188,447

METHOD OF WELDING Original Filed Sept. 16, 1957 INVENTORS Robert D. Bremer Alfred J. Sacksfeder 4, 28 Attorney United States Patent 3,188,447 METHOD 0F WELDING Robert D. Bremer and Alfred J. Sacksteder, Dayton, one,

This application is a division of our copending application Serial No. 684,159 for Domestic Appliance, filed September 16, 1957, now Patent No. 3,068,304, dated December 11, 1962. It relates to a method of welding brackets to metal means such as sheathed electric surface heaters.

Recently, there has been developed an unusually thin form of sheathed tubular surface heaters having sui'ficiently elasticity to contorm to the bottom of the p an's to be supported and heated thereon. There has been a problem in arranging the proper support for such heaters without diminishing their ability to conform to the bottom surface of the pan.

It is an object of this invention to provide a structure and method which will readily and simply resiliently fasten both coils of a two-coil thin tubular sheathed sur face heater to its support.

It is another object of this invention to provide an easy method of welding and a simple welded structure for welding either a single or a two-coil tubular sheathed surface heater to its support without burning or damaging or causing leakage of the sheath.

These and other objects are attained in the form shown in the drawing in which a two-coil thin tubular sheathed surface heater is mounted upon a five-armed spider of stainless steel strip. The bottoms of several of the arms are notched at one or more places to receive loops of a resistance wire bracket. The opposite ends of these wire brackets are welded to either the same or adjacent turn-s of the two coils. The resistance wire has a high electrical resistance and melts at a lower temperature than the stainless iron sheath.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, where in a preferred form of the present invention is clearly shown.

In the drawings:

FIGURE 1 is a top view of a surface heater embodying one form of my invention;

FIGURE 2 is a fragmentary vertical sectional view taken along the line 2-2 of FIGURE 1; and 4 FIGURE 3 is a fragmentary vertical sectional view taken along the line 33 of FIGURE 2.

Referring now to the drawing, there is shown a flanged rim 20 havingan upper outwardly extending ornamental flange adapted to extend over and rest upon the portion "of the range top 22 bordering the flanged opening 24.

The rim 20 is provided with an inner supporting ledge 26 upon which rests the outwardly extending flange of the drip pan 28. Supported upon the top of the flange of the drip pan 28 is a five-armed support 30 of stainless steel strip which has round-nosed projections 32 at the ends of the arms extending beneath integral projections 34 on the rim. The projections 32 and 34 interengage to resilientlyhold the rim 20, the support 30 and the drip pan 28 together.

Above the support 30 is a two-coil electric surface heater of the thin tubular sheath type including an outer coil 33 of two turns or loops having the end portions 35 and 36 extending to the right beneath the rim 2% and an inner coil 38 of four turns or loops having the terminals 40 and 42 extending outwardly to the right under the rim 20. These coils 33 and 38 are both of the thin tubular sheath type, each containing a coiled resistance wire 44 and 46 embedded in solid electrical insulation 48' and 50, such as magnesium oxide. The magnesium oxide of each are enclosed in a thin tubular sheath 52 and 54 of a suitable nickel chromium iron, such as Incoloy having a composition of about 30-35% nickel, chromium and the remainder iron and melting at a temperature of about 2,51'5 F. This sheath has a diameter of .230" and a wall thickness of .022". Instead of this, an alloy of chromium, 12% nickel and the remainder iron, melting at between 2550 and 2650 F. may also be used. I

To provide a simple method of resiliently attaching the coils 33 and 38 to the support 30, at least one or two of the arms of the support adjacent to and opposite the terminals 35, 36, and 42 are each provided with a notch 56 on their lower edge between the adjacent turns of the coils 33 and 38. These notches or slots 56 each receive the resilient yoke of a resistance wire alloy bracket 58 of the configuration shown in FIGURE 3 With the wire extending from the notch along both sides of the arm in the form of a U and having one end portion 60 extending initially radially and then at right angles transverse to and laterally beneath the coil 33 and the op posite end portion 62 extending initially radially and then at right angles transversely to and laterally beneath the adjacent turn of the coil 38. This configuration of successive right angle bends in different planes allows lateral and upward movement of the coils 33 and 38 relative to the support 30. This wire is suitable for welding and has a high electrical resistance. It has a composition of about 60% nickel, 16% chromium, with the remainder iron, and has a melting point of 2460 F. and a diameter of .057. The transverse opposite end portions 60 and 62 of these wire'brackets 58 are resistance welded to the adjacent bottom portions of the adjacent turns -of the heaters 33 and 38 so as to connect with one bracket both coils to two of the arms of the support 30.

'This welding is preferably accomplished while the two coils 33 and 33, the support 30 and the brackets 58 and 66 are inverted upon an electrically conductive metal welding support. The two electrodes 64 and 65 of the welder engage and press the ends 62 and 60 of the transverse vportions of each of the brackets 58 against the adjacent surface of the coils 33 and 38 as if FIGURE 3 were inverted. At a suitable potential, the AC. weldin current is applied to the electrodes 64 and 65 and flows from the electrode 64 through both adjacent end 60 of the bracket 58 and the sheath of the heater 33 to and through the welding support and the adjacent and contacting portions of the sheath of the heater 33 and the opposite end 60 of the bracket 58 to the second electrode 65. To achieve the desired heat balance for welding, the current flow through the sheaths is reduced by a parallel current flow directly through the continuous wire bracket 53 between the electrodes 64 and 65 for heating the bracket 58. In addition, the wire size of the brackets and their electrical resistance and length are so chosen that the contacting surfaces of the brackets reach welding temperatures slightly before or at the same time as the sheath. This welding method particularly prevents any burning, cracks or other dam-age to the sheaths adjacent the welds which might cause leakage and also because of the reduced current flow through the sheath minimizes marring of the top surface of the coils.

Because of the higher resistivity and the lower meltis made without any danger of overheating and creating tiny holes in the sheath which would permit leak-age and Without any burning or other damage to the sheath. The brackets are inexpenisve, readily assembled and welded. The yoke of th'e'brackets 58 need not extend to the closed end of the slots 56 so that the coils 33 and 38 have a limited amount of movement in the vertical direction relative to the support 30 so that the coils may readily accommodate themselves to irregularities and particularly "lack of flatness of the bottom of pans and other utensils which may be used t'hereon. To pre- 7 vent; the bending of the outer turn or loop of the coil 33, one or more additional wire brackets 66 of the same material as the brackets 58 may be looped through the notches 68 in the bot-toms of one or more of the arms of the support 30 opposite the terminals 35, 3,6, 40 and 42. The ends of the, brackets 66 are welded to the outer turn or loop of the coil 33 by the same Welding process used for the brackets 58. Each end of each bracket tie is provided with two right angle bends in different planes to'provide resiliency for absorbing the termal expansion of the coils 33 and 38. The top surface of the sheaths may be flattened as shown particularly in'F-IG- URE 2 so as to provide greater surface area contact and also to compact the solid electrical insulation surrounding the resistance wire conductors 44 and 46.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, as may come Within the scope of the claims which follow.

What isclaimed is as follows: I 1. The method of welding the opposite end portions of a metal bracket to metaltubing which includes the steps of selecting a metal bracket whose cross-sectional size, electrical resistance and length is such as to effect a welding temlperature at the contacting surfaces of said bracket with said tubing at least ass'oon as a Welding temperature is reached at the contacting surfaces of said tubing, applying a welding electrode to each'end portion of the bracket to force the end portions into contact with the metal tubing While the metal tubing is supported upon a support of metal, and while the end portions are forced against said metal tubing applying a welding current'at'a suitable potential through said 4,. electrodes to said end port-ions to cause sufiicient current to flow through the bracket to bring its ends to welding temperature at least as soon as the contacted surfaces of the metal tubing are raised to welding temperature by the flow of current through the adjacent and contacting surfaces of the bracket and metal tubing and said support.

2. The method of welding the opposite end portions of a relatively thick metal wire bracket to thinner metal tubing which includes the steps of selecting ametal bracket whose wire size, e'lectricalresist'ance and length is such as to eflfect a welding temperature at the contacting surfaces of said bracket with said tubing at least as soon as a welding temperature is reached at the contacting surfaces of said tubing, applying a welding electrode to each end portion of the bracket to force the end portions into con-tact with the metal tubing while the metal tubing is supported upon a support of metal, and while the end portions are forced against said metal tubing applying a Welding current at a suitable potential through said electrodes to said end portions to cause-sufii'cient current to flow through the bracket to bring its ends to Welding temperature at least as soon'as the contacted surfaces of the metal tubing. are raised to' Welding tem- I peratur'e by the flow of current through the adjacent and contacting surfaces of the bracket and metaltubing and said support. 1 7

References Cited by the Examiner Mantz: German application 1,001,361,,published Jan nary 24, 19 57, KL.21;a4.

RICHARD M. WOOD, Primary Examiner, 

1. THE METHOD OF WELDING THE OPPOSITE END PORTIONS OF A METAL BRACKET TO METAL TUBING WHICH INCLUDES THE STEPS OF SELECTING A METAL BRACKET WHOSE CROSS-SECTIONAL SIZE, ELECTRICAL RESISTANCE AND LENGTH IS SUCH AS TO EFFECT A WELDING TEMPERATURE AT THE CONTACTING SURFACES OF SAID BRACKET WITH SAID TUBING AT LEAST AS SOON AS A WELDING TEMPERATURE IS REACHED AT THE CONTACTING SURFACES OF SAID TUBING, APPLYING A WELDING ELECTRODE TO EACH END PROTION OF THE BRACKET TO FORCE THE END PORTIONS INTO CONTACT WITH THE METAL TUBING WHILE THE METAL TUBING IS SUPPORTED UPON A SUPPORT OF METAL, AND WHILE THE END PORTIONS ARE FORCED AGAINST SAID METAL TUBING APPLYING A WELDING CURRENT AT A SUITABLE POTENTIAL THROUGH SAID ELECTRODES TO SAID END PORTIONS TO CAUSE SUFFICIENT CURCENT TO FLOW THROUGH THE BRACKET TO BRING ITS ENDS TO WELDING TEMPERATURE AT LEAST AS SOON AS THE CONTACTED SURFACES OF THE METAL TUBING ARE RAISED TO WELDING TEMPERATURE BY THE FLOW OF CURRENT THROUGH THE ADJACENT AND CONTACTING SURFACES OF THE BRACKET AND METAL TUBING AND SAID SUPPORT. 